Drive trains of hybrid vehicles comprise multiple drive assemblies, namely, a first drive assembly formed as an internal combustion engine, a second drive assembly formed as an electric motor, a transmission, and an output. With such a drive train, the first drive assembly acts on a first transmission shaft of the transmission, whereas the second drive assembly acts on a second, different transmission shaft of the transmission. The transmission of the drive assembly includes multiple shift elements, which are typically designed as frictional-locking shift elements, such as, for example, clutches or brakes. At the output of the drive train, an output torque depending on a driver's requested torque is provided. In defined operating situations of such a drive train, it is necessary to open a previously locked shift element of the transmission. If a frictional-locking shift element is to be opened, this can occur in a simple manner by the fact that the frictional-locking shift element is brought into slip. This gives rise to friction torques or drag torques, which have negative effects on consumption. Therefore, in transmissions of a drive train, frictional-locking shift elements are being increasingly replaced by positive-locking shift elements, such as claw shift elements. However, such positive-locking shift elements, so that they can be opened, must be transferred into a load-free state or placed without load.
DE 10 2011 080 068 A1 discloses a method for performing a gearshift in a transmission of a power train, with which a first drive assembly formed as an internal combustion engine acts on a transmission input shaft and a second drive assembly formed as an electric motor acts on a transmission shaft provided by a planetary gear stage of the transmission. For executing a power shift, it is known to place a shift element to be disengaged in a load-free condition. Time is required to place the shift element in such a condition; this increases the time required to carry out the gearshift.